High performance ejector enhanced by heat exchanger in solid oxide fuel cell anode recirculation system

Abstract

The ejector-based recirculation system has a promising application in the solid oxide fuel cell (SOFC) with the advantages of no parasitic power, small size, lightweight, and easy maintenance compared with the pump-driven system. However, it is difficult for the ejector to satisfy the requirements of high backpressure and the high-entrainment ratio at the same time in the SOFC system. To overcome the problems, a heat exchanger enhanced SOFC anode recirculation system is proposed for improving the performance of the ejector whose primary flow is heated by the second flow through a heat exchanger in the high-pressure ratio of 1.08. The flow characteristic and performance of the ejector are investigated with the variation of the inlet temperatures by computer fluid dynamics (CFD) and the experiment. The results show that the entrainment ratio ω and the steam to carbon ratio (STCR) are improved respectively from 2.37 to 7.73 and 0.74 to 2.11 at the pressure ratio of 1.08 compared with the condition without the heat transfer. Meanwhile, the current density and power of the SOFC are increased from 414.68 A/m2 to 552.20 A/m2 and 34.84 kW to 45.88 kW, and the voltage of the SOFC has practically maintained at 0.88 V. The improvement of the SOFC power is up to 30 %. The exchanger enhanced ejector recirculation system provides an effective way for improving the performance of the SOFC system.